sysdeps/unix/sysv/linux/s390/elision-conf.c

   1 /* Lock elision tunable parameters.
   2    Copyright (C) 2014-2015 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <config.h>
  20 #include <pthreadP.h>
  21 #include <elision-conf.h>
  22 #include <unistd.h>
  23 #include <dl-procinfo.h>
  24
  25 /* Reasonable initial tuning values, may be revised in the future.
  26    This is a conservative initial value.  */
  27
  28 struct elision_config __elision_aconf =
  29   {
  30     /* How often to not attempt to use elision if a transaction aborted
  31        because the lock is already acquired.  Expressed in number of lock
  32        acquisition attempts.  */
  33     .skip_lock_busy = 3,
  34     /* How often to not attempt to use elision if a transaction aborted due
  35        to reasons other than other threads' memory accesses.  Expressed in
  36        number of lock acquisition attempts.  */
  37     .skip_lock_internal_abort = 3,
  38     /* How often to not attempt to use elision if a lock used up all retries
  39        without success.  Expressed in number of lock acquisition attempts.  */
  40     .skip_lock_out_of_tbegin_retries = 3,
  41     /* How often we try using elision if there is chance for the transaction
  42        to finish execution (e.g., it wasn't aborted due to the lock being
  43        already acquired.  */
  44     .try_tbegin = 3,
  45     /* Same as SKIP_LOCK_INTERNAL_ABORT but for trylock.  */
  46     .skip_trylock_internal_abort = 3,
  47   };
  48
  49 /* Force elision for all new locks.  This is used to decide whether existing
  50    DEFAULT locks should be automatically upgraded to elision in
  51    pthread_mutex_lock().  Disabled for suid programs.  Only used when elision
  52    is available.  */
  53
  54 int __pthread_force_elision attribute_hidden = 0;
  55
  56 /* Initialize elison.  */
  57
  58 static void
  59 elision_init (int argc __attribute__ ((unused)),
  60               char **argv  __attribute__ ((unused)),
  61               char **environ)
  62 {
  63   /* Set when the CPU and the kernel supports transactional execution.
  64      When false elision is never attempted.  */
  65   int elision_available = (GLRO (dl_hwcap) & HWCAP_S390_TE) ? 1 : 0;
  66
  67   __pthread_force_elision = __libc_enable_secure ? 0 : elision_available;
  68 }
  69
  70 #ifdef SHARED
  71 # define INIT_SECTION ".init_array"
  72 # define MAYBE_CONST
  73 #else
  74 # define INIT_SECTION ".preinit_array"
  75 # define MAYBE_CONST const
  76 #endif
  77
  78 void (*MAYBE_CONST __pthread_init_array []) (int, char **, char **)
  79   __attribute__ ((section (INIT_SECTION), aligned (sizeof (void *)))) =
  80 {
  81   &elision_init
  82 };